1. Field of the Invention
The present invention relates to an image display device in which a light emitting element, such as an organic EL device, is used in a pixel. Particularly, the invention relates to an active matrix type image display device for driving light emitting elements by scanning transistors formed in pixels, respectively. More particularly, the invention relates to a technique for reducing the number of plural scanning lines which are provided in rows of pixels.
2. Description of the Related Art
In an image display device, such as a liquid crystal display device, a large number of liquid crystal elements are disposed in a matrix and a transmission intensity or a reflection intensity of an incident light is controlled every pixel in accordance with information on an image to be displayed, thereby displaying the image on a screen. Although this similarly applies to an organic EL display device in which an organic EL element is used in a pixel, unlike a liquid crystal element, the organic EL element is a self light emitting element. For this reason, the organic EL display device, for example, is advantageous in that an image displayed thereon has higher visibility than that in the liquid crystal display device, a backlight is unnecessary, and a response speed is high. Moreover, the organic EL display device is much more different from the liquid crystal display device or the like which is of a voltage control type in that it is of a so-called current control type because a luminance level (gradation) of each of the light emitting elements can be controlled by a value of a current caused to flow through a corresponding one of the light emitting elements.
For the organic EL display device, similarly to the liquid crystal display device, a simple matrix system and an active matrix system are adopted as a system for driving the organic EL display device. The former involves such a problem that it is difficult to realize a large display device having a high definition, although it is simple in constitution. For this reason, at present, the organic EL display device utilizing the active matrix system is actively developed. According to the active matrix system, a current which is caused to flow through a light emitting element provided inside each of pixel circuits is controlled by an active element (generally a thin film transistor (TFT)) provided inside a corresponding one of the pixel circuits. The organic EL display device utilizing the active matrix system, for example, is disclosed in Japanese Patent Laid-Open Nos. 2003-255856, 2003-271095, 2004-133240, 2004-029791, and 2004-093682.